In many types of display units it is desirable to provide masking of those zones of the panel of the unit which does not contain information content, or to provide masking of selected zones to obtain special effects. Masking of display zones which do not contain information, as previously proposed, was done by applying external masks to the display panels. In case of LCD units, the masks are applied to the outer glass or front polarizer surface. The minimum thickness of the glasses which retain the liquid crystal cannot be passed. It is thus difficult to apply masking which is precisely aligned with LCD panels, and in which reading is completely free of parallax. Applying masking to the outside requires additional manufacturing steps, which increases the cost of the display unit.